Action Gap Backflow Preventer for DEMA Units

This is the safety device that makes a chemical proportioner legal to connect to a building's water supply. The DEMA 16.30 mounts inline above the eductor and creates a physical break in the water path, so if pressure in the main ever drops, concentrated chemical cannot be siphoned backward into the potable supply. It does nothing for cleaning performance and everything for the thing that happens when a hydrant opens down the street while your unit is drawing chemical.

It carries ASSE 1055B certification, which is the standard written specifically for chemical dispensers with integral backflow protection, and connects with 3/4" hose thread at both the inlet and the outlet. It sits directly above the green 1/4" eductor valve on the 1 GPM blend centers we carry. See the rest of the DEMA range for the other service parts on these units.

What Makes it Great:

🛡️ ASSE 1055B Certified: Meets the standard written for chemical dispensers with integral backflow protection, which is what an inspector is looking for on a proportioner installation.

🚰 Protects the Potable Supply: Creates a physical break so a pressure drop in the main cannot pull concentrated chemical back into the building's drinking water.

🔩 3/4" Hose Thread Both Ends: Standard GHT in and out, so it threads into the existing plumbing without adapters or rework.

🧩 Genuine DEMA Assembly: The same component these proportioners ship with from the factory, so certification and fit both carry over on replacement.

Frequently Asked Questions

What does a backflow preventer actually do?

It stops water from traveling the wrong direction. Normally your supply pushes water through the unit and out. If pressure in the main suddenly drops, from a water main break, a hydrant opening, or a large draw elsewhere in the building, the flow can briefly reverse. Without protection, that reversal pulls whatever is in the line backward, which on a chemical proportioner means concentrated chemical heading toward the drinking water.

Why does a chemical dispenser specifically need one?

Because of what it is connected to on both ends. A proportioner is deliberately introducing concentrated chemical into a potable water line, which plumbing codes classify as a high hazard connection. Most equipment poses a low hazard if it backflows. This poses a health hazard, which is why a dedicated standard exists for it and why the device is built into the unit rather than being optional.

What does ASSE 1055B mean?

ASSE 1055 is the performance standard for chemical dispensers with integral backflow protection. The B designation covers the backflow preventer component itself when it is supplied as a separate assembly rather than built into the dispenser body. In practical terms it is third-party verification that the device does what it claims under the failure conditions the standard tests for.

Mine weeps from the vent. Can I just take it off?

No. Weeping usually means scale or debris is keeping the internal seal from closing properly, and the correct response is replacement. Removing it or plugging the vent defeats the only thing standing between concentrated chemical and the building's water supply, and it will fail inspection. Local plumbing code governs the specifics of your installation, so check with your inspector if you are unsure, but running a proportioner without backflow protection is not an option anywhere.

Is this the same part as the eductor?

No, and they sit right next to each other, which is why they get confused. The eductor is the venturi below this assembly that pulls concentrate into the water stream. This is the safety device above it that keeps that mixture from going backward. One handles dilution, the other handles protection, and replacing the wrong one will not fix the symptom you are chasing.